The present invention relates to a method and apparatus for winding a continuously advancing yarn into a package.
When winding a yarn into a package, it is always attempted to obtain a stable package build, a uniform packing density, as well as satisfactory unwinding characteristics during a later further processing stage. In this connection, the end faces of such packages may extend in a normal plane, so that cylindrical packages are obtained, or they may be inclined relative to this normal plane, so that a biconical package is formed. In the winding of packages, the problem arises that the yarn reversal causes a mass accumulation at the package edges, which leads to hard package edges or a bulgy package edge.
It is known both from U.S. Pat. No. 4,659,027 and from EP 0 235 557 that for purposes of avoiding the bulges at the package ends, the traverse stroke may be changed by modifying the stroke, i.e., by periodically shortening and lengthening the traverse stroke in the end region of the package edges, thereby displacing the reversal point at the package edge. However, the yarn deposit in each of the reversal points is the same, so that the yarns are distributed at the package ends as a function of the stroke modification frequency. This procedure has shown that at a small stroke modification frequency the end faces of the package are softer in comparison with a package that is wound at a high stroke modification frequency.
In an effort of avoiding excessively high package edges, a further disadvantage is found in that the traverse stroke must be shortened by as much as 20 mm during the stroke modification. While this shortening prevents a buildup of edges, the yarn is deposited irregularly and, thus, an irregular packing density is incurred in the edge region, which leads likewise to soft end faces of the package. Depending on the kind of further processing, this is undesirable, since soft packages are more susceptible to damage than hard packages.
Furthermore, the alternate shortening or lengthening of the traverse stroke has the disadvantage that the yarn guide reciprocating the yarn is urged to cover alternatingly a long and a short traverse distance.
It is accordingly an object of the present invention to provide a method and apparatus for winding an advancing yarn into a package, which corrects the yarn deposit in the edge region irrespective of a stroke modification and irrespective of the length of the traverse stroke.